Skimming device for clarification tanks



June 15, 1954 Filed Feb. 24, 1953 4 Sheets-Sheet 1 H. B. COULTER SKIMMING DEVICE FOR CLARIFICATION TANKS June l5, 1954 Filed Feb. 24, 1955 INI/ENTOR.

Harold B. Coulter TTORNE Y June 15, 1954 H. B. COULTER SKIMMING DEVICE FOR CLARIFICATION TANKS 4 Sheets-Sheet 3 y Filed Feb. 24, 1953 JNI/ENTOR.

' Harold B. Coulter ,HTORN'EY Jime 15,"1954 H. B. COULTER SKIrvm/IINGA DEVICE FOR CLARIFICATION TANKS Filed Feb. 24, 1955 4 Sheets-Sheet 4 INI/ENTOR.

Harold B. Coulter www3@ ArroRNEY Patented June 15, 1954 UNITED STATES AENT OFFICE SKIMMING DEVICE FOR CLARIFICATION TANKS Harold B. Coulter, Larchmont, N. Y., assignor to The Dorr Company, Stamford, Conn., a corporation of Connecticut 4 Claims.

This invention relates to scum skimming devices or equipment for continuously operating clarier or sedimentation tanks. A solids-carrying liquid is fed to such tanks at the center while settled matter or sludge is withdrawn from the bottom, with claried liquid overflowing into a peripheral launder provided at the top of the tank. Such continuously operating clarier tanks or units have a rotary mechanism which, while rotating, conveys the sludge over the tank bottom to a point of discharge or pocket or sump whence the sludge is usually pumped to a place of disposal outside the tank.

Scum skimming devices for such clarier tanks comprise a scum skimming blade or blades rotating with the raking mechanism, and a stationary scum-receiving trough extending from the periphery of the tank radially inwardly along the overflow level of the liquid. Heretofore, the skimmer blade would deliver collected scum when passing across the receiving trough whence the scum ilows or is pumped to a place of disposal outside the tank.

A problem arises with respect to the disposition and arrangement of the skimming device, where both the trough as well as the skimmer means above are of considerable length as in tanks of large diameter and where they are required to extend substantially along the full length of the radius of the tank, such problem being due to the difficulty of supporting a long free cantilevering length of trough from the wall of the tank. Similarly, it is diflicult to support a corresponding length of skimming means from the central portion of the rotary raking structure.

According to this invention such diiiiculty is met and overcome by taking advantage of an overhead stationary truss or bridge structure often provided in such tank units, and by employing it as a mounting to support or suspend therefrom a stationary scum receiving trough, while providing upstanding skimmer means yieldably mounted upon and carried by one of the raking arms, in such a manner that their emerging upper free edge portion will sweep the scum towards and into the scum trough or channel incident to the. rotation of the raking structure, then to continue yieldingly and submergedly underneath the scum trough, only to emerge again and thus to automatically re-assume scum-skimming position as the raking structure continues on another cyclone of scum skimming rotation.

An overhead supporting structure for the stationary scum receiving trough may have a variety of forms, for example, the form of a diametrically extending overhead construction sometimes employed for rotatably supporting the raking structure with its driving mechanism, or it may be in the form of a bridge structure employed in tank units Where the raking structure is rotatably supported not upon the bridge structure proper, but upon a center pier, and the bridge structure extends from the tank wall to the center pier.

According to one feature, the skimmer means comprise a plurality of skimmer elements or blade members disposed in end-tc-end relationship with respect to one another, and pivotally mounted upon the raking arm, while so weighted as to be normally urged into upright active scumskimming position, but to tiltably yield into an inclined position upon contact with the trough to pass submergedly underneath the trough.

Further particularized, a feature provides a bridging connection of flexible sheet material between the mutually adjoining ends of a pair of skimmer blade members.

According to another feature, the weighted tiltabe skimmer elements are cooperatively associated with a scum trough having the form of a horizontal pipe provided with longitudinal scum receiving openings at one side thereof, which trough or pipe is rotatably positionable in a manner to adjust, the scum receiving openings with respect to the overflow level of the liquid body in the tank.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and notrestrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims, or of forms that are their functional as well as conjointly cooperative equivalents are therefore intended to be embraced by those claims.

In the drawings,

Figure 1 is an overall diagrammatic vertical sectional view of a center pier type tank unit with the novel scum skimming devices embodied therein.

Figure 2 is an enlarged View of the tank unit of Figure l showing the construction thereof and of the skimming devices more fully implemented.

Figure 2a is a detail top View taken on line 2er-2a in Figure 2, showing a flexible bridging between mutually adjoining ends of a pair of skimming blade members.

Figure 3 is a partial plan view of the tank unit 3 taken on line 3-3 of Figure 2, including a View of t ie bridge construction and center pier, and of the scum receiving and discharge trough associated with the bridge construction.

Figure 4 is a vertical detail section of the bridge construction and skimming devices taken on line A-d of Figure 2.

Figure 5 is a side view taken on line 5 5 of Figure 4.

According to Figure 1, the invention is embodied in a tank unit of the center pier type comprising a bottom I 0, a wall II, provided with eilluent overow launder I2, the overflow level being denned by a weir I3 which is associated with a customary cylindrical scum baille Ill spaced inwardly from the weir and substantially concentric therewith. The overow launder I2 is shown to have a discharge connection I5 leading to a discharge conduit I6. From the center of the tank bottom there rises a hollow pier I'I supporting a rotary raking structure I8 which in turn comprises a structural vertical cage construction I 9 the top end of which has rotary bearing support upon the top end portion of the pier. A pair of raking arms 2B and 2I shown in the form of truss members extend in opposite directions with respect to each other from the lower end portion of the cage Construction I9, the rake arms being diagrammatically indicated to comprise horizontal component members 22 and 23, vertical component members 24, and diagonal members 25, with usual sedimentation engaging blades 26 provided at the underside of these truss members.

An influent conduit 21 extends underneath the tank to carry feed liquid to the foot end of the pier i?, so that the liquid upiiowing in the pier may be issued from feed openings 28 provided at the top end portion of the pier. A usual cylindrical feedwell 29 concentrically surrounds the upper portion of the pier and feed openings 28 such feed-well here being mounted upon the rake structure I3 to rotate therewith. A sludge collecting sump or pocket 30 is provided at the foot end of the pier to which the settled matter or sludge upon the tank bottom is conveyed by the rotation of rake structure I8, and from which pocket sludge is withdrawn or pumped to a place of disposal as indicated by a sludge discharge pipe SI. A stationary bridge construction 32 leads from the tank wall to an operating platform 33 upon the top end of the pier which platform is shown to carry a motorized driving mechanism or drive unit indicated at 34 for rotating the rake structure I8.

The scum skimming device according to this invention is here diagrammatically indicated to include a scum receiving trough in the form of a horizontal pipe 35 supported from and mounted at the underside of bridge construction 32 and shown to lead into a separate discharge conduit indicated at S. Points of support for this scum receiving pipe are indicated at 36, horizontally elongated scum receiving openings 31 in the pipe are indicated to extend along one side of the pipe and between respective supporting points 35. The supports 35 permit rotational adjustment of pipe 35, and a device for executing such adjustment is indicated at D mounted upon the bridge construction 32.

Skimmer means carried by the rake arm 2| are diagrammatically indicated in the form of a series of skimmer blades 38 disposed in an endto-end relationship with respect to one another and so as to extend horizontally above and along the arms 2|, yet so mounted thereon as to be' yieldable or swingable about a horizontal axis indicated at A. That is to say, upright supporting means indicated as by upright supporting members 39 rise from the arm structure 2| to provide at the top end portions pivotal bearing means for the individually swingable skimmer blades 33. The scum skimming device and other details will be shown and described in greater detail and more fully implemented in connection with the remaining Figures 2, 2a, 3, 4 and 5.

In Figure 2, a tank being similar to that of Figure l although with intermediate portions broken away so it appears horizontally foreshortened, comprises a bottom I, a wall II', provided with eilluent overflow launder I2', the overiiow level being deiined by a weir I3', having a customary cylindrical scum baffle Ill spaced inwardly therefrom and concentrically therewith. The overflow launder has a discharge connection I5 leading to discharge conduit I6. From the center o the tank bottom there rises a pier I1' supporting a rotary rake structure I3 which in turn comprises a central vertical cage construction i9 the top end of which has a rotary bearing supported upon the top end portion of the pier. A pair of rake arms 2c and 2l in the form of truss structures extend in opposite directions with respect to each other from the lower end of the cage construction I9', which rake arms are indicated to comprise horizontal component members 22', and 23', vertical members 2Q', and diagonal members 25', with the usual sediment engaging blades 26' provided at and fixed to the underside of these truss structures or raking' arms. An influent conduit 2l' extends underneath the tank to carry feed liquid to the foot end of the hollow pier so that the liquid upflowing in the pier may issue from feed openings 28" provided at the top end portion of the pier. A usual cylindrical feedwell 29 concentrically surrounds the upper end portion of the pier and thus the feed openings 2B', such feedwell being here mounted upon the rake structure I8 to rotate therewith. v

A sludge collecting sump or pocket 35 is provided at the foot end of the pier to which sediment is conveyed over the tank bottom by the rotation of the structure I8', and from which pocket sludge is withdrawn or pumped as is indicated by a sludge discharge pipe 3| leading from the sump.

A stationary bridge construction 32 leads from the tank wall to an operating platform 33 atop the pier which platform carries motorized driving mechanism or a motor drive unit 34 for rotating the rake structure I8.

A scum receiving trough in the form of a horizontal pipe 35 is supported from and mounted at the underside of bridge construction 32 and is shown to lead into a separate discharge conduit S. Points of support for the pipe 35' are in the form of bearing members indicated at 35' allowing for rotational adjustment of the pipe while horizontally elongated lateral scum receiving openings 3l" in the pipe are indicated to extend between respective bearing members St.

A device D for rotatably adjusting the pipe 35 in bearing members 36', that is to say, a device for adjusting the scum receiving openings 37 relative to the liquid overflow level comprise a pair of upper pulleys d and 4I, a pair of lower pulleys A2 and 43, bracket means 44 mounting the pulleys upon the bridge construction 32', and

linear ii'exible motion transmitting means or pull wires i and 46 engaging these pulleys and attached to and anchored upon respective sides of pipe 35 in such a manner that joint rotation of the upper pulleys in either the one or the other direction will rotate the pipe 35 in a corresponding direction to make the desired adjustment above referred to.

Skimmer blades 38 are carried by the rake arm 2 I disposed in end-to-end relationship with respect to one another to extend horizontally above and along the arm 2 l said skimmer blades being furthermore mounted so as to be swingable or yieldable about a horizontal axis A. Upright members 39 rise from the rake arm structure I8 for thus swingably supporting the skimmer blades 39.

Provision is made for preventing the escape of floating substance through a clearance existing between the mutually adjoining ends of a pair of skimmer blade members 38 of Figure 1 or 38 of Figure 2. Therefore, the detail Figure 2a shows in plan view a loop-shaped bridging strip B of flexible material such as plastic sheeting, fastened to the respective ends E1 and E2 of the skimmer blades.

Figures d and 5 are ydetails of the scum skimming device and of some of its associated structures such as the rake arm structure 2| and cf the bridge construction 32". rThat is to say, the rake arm structure 2l" is in the form of a box type truss structure having internal diagonal transverse bracing 4l. Upright members 39 rise from the top of this truss structure (corresponding to the member 39 in Figure 2 and 39 in Figure l) which upright members have inclined bracing members 48 and 49 between them and the respective upper corners of the box type structure 2l". A skimmer blade structure here designated as 33" (corresponding to the member diagrammatically shown at 38' in Figure 2 and member 38 in Figure 1) has transverse vertical arms 58 whereby a skimmer blade B proper is pivotally mounted as at pivot points 5| upon the respective upright member 39". Thus, the skimmer structure 38 of Figure 4 comprises an upper arm portion p1 extending upwardly from pivot point 5l, and a lower arm portion p2 extending downwardly from pivot point 5|, the latter portion p2 being provided with a weight member 52 preferably adjustable along the portion p2. The skimmer structure of 38 has an upper portion d of the skimmer blade B proper normally emerging from and above the liquid level L.

The bridge construction 32 according to detail Figure 4 comprises a pair of horizontal structural channel members 53 and 54 interconnected at the top as by top plates 55 and interconnected at the bottom as by transverse tie members 56 which later in turn serve for mounting the supporting or bearing means 35 for pipe 35" comprise a U-shaped cradle member 51 having upright shank portions 5'ia and 51h the end portionsl of which are fastened and fixed to a pair of bracket members 58 and 59 which in turn are fixed to and extend downwardly from a respective transverse tie member 56. A confining strip or saddle element 60 extends and is fastened to the upright shanks 58 and 59 respectively of the cradle member, holding the pipe 35 in place although rotatably within the cradle member 51.

Actuating means for rotatably adjusting the pipe 35" comprise an upper pair of pulleys 40 and 4I and a lower pair of pulleys 42 and 43", both pairs of pulleys being mounted upon a bracket construction C fastened to the channel member 53 as Well as to a railing construction R shown to constitute part of the bridge construction 32". A flexible motion transmitting element such as a pull wire 8| engages upon upper pulley 40" as well as upon lower pulley 42 and has its lower end anchored upon a lug 62 provided upon the underside of pipe 35". A second pull wire 63 engages upon the other upper pulley 4l as Well as upon the lower pulley 43 and has its lower end attached to an anchoring lug 64 provided upon the top side of pipe 35". Thus by turning a handle H either in the direction of arrow Ri or of arrow R2 (see Figure 4) the pipe 35 can be adjusted rotationally in corresponding directions. By turning the handle in the direction of arrow R1 the pipe' will turn in the direction of R3, whereas by turning the handle in the direction of R2 the pipe will turn in the direction of arrow R4. Instead of the pulleys and the pull wires 6I and 62, any equivalent actuating means for example, sprockets and chains may be employed.

The operation of the skimming device is substantially self explanatory from the drawing iigures, and particularly from Figure 4. Where the iniluent liquid comprises, for example, a mixture of oil, water, and settleable solids, the liquid entering through iniiuent conduit 2l (see Figure 2) rises through center pier Il to the discharge openings 28 at the top end thereof, thence fiows radially in all directions into the space dened by the cylindrical feed well 29. The feed well gives the flow a downward direction to encourage the solids to settle, while the waters along with the lighter component such as oil continuesI to flow radially in all directions through the annular zone of quiescence between the feedwell and the overflow I3. Within this quiescent zone the lighter liquid component or oil has an opportunity to, and does rise to the surface so that a oating layer of oil will be conned within the annular area between the feedwell 29' and the cylindrical bale lll'.

The raking structure I3 rotates being driven by the drive unit 34', engages settled solids to convey them over the tank bottom inwardly towards the center pier and into the pocket 38 for withdrawal; at the same time the skimmer blades 38 (in Figure 2) or blade B" (in Figure 4) in their then upright position convey the floating component or o-il along the liquid surface to the receiving pipe 35 as is indicated by arrow W in Figure 3. Thus with each cycle of rotation of the raking structure there is delivered into the receiving pipe 35' by way of the receiving openings, 31 therein a quantity of the floating water or oil, namely substantially the quantity that accumulates at the surface within the time of a single revolution of the raking structure. The oil or floating matter is thus delivered through and from the receiving pipe 35 into the discharge conduit S for further disposal. From Figure 4 it will be seen that whenever the skimming blades B in delivering the oil for discharge reach and enter into contact with the receiving pipe 35', the continued motion of the raking structure will cause the blades 38 to be tilted or deflected rearwardly as indicated by the dot-and-dash line position of the blade in Figure 4, and thus to duck under and past the receiving pipe, thereafter to return to its normal vertical active position as the raking structure commences a new cycle of rotation. Since the skimming blades 38 are connected with one another endwise by such exible 7 elements as the loops B (see Figures 2 and 2a) it will be seen that the sum total of the blades act as one, so that the iloating oil is conveyed effectively towards the receiving pipe 35', namely Without escape through the clearances between respective endwise adjoining ends of the blades.

I claim:

1. In a liquid treatment tank for clarifying liquid, supply means for feeding to the tank liquid to be clarified, having peripheral overflow means determining the liquid level of a body of liquid in the tank, a rotary sediment raking structure provided with at least a pair of radially extending rake arms, drive means for rotating the raking structure, and having means for discharging sediment from the tank bottom, a skimming device comprising a scum receiving trough extending radially of the tank and stationary overhead supporting means therefor, and skimmer means comprising a skimmer blade element and means for yieldably mounting the same upon one of said arms, whereby said blade element is normally urged into active scum conveying condition with its free upper edge portion emerged from the liquid in the tank to deliver scum to and into said trough and adapted to yield upon contact with said trough incident to the rotation of said raking structure for submergedly passing underneath the trough and thereafter to be urged to re-assume its emerged scum conveying condition.

. 2. The skimming device according to claim 1, in which said mounting means are characterized 8 thereby that the blade element is pivotally and tiltably mounted and is weighted for urging the blade into active scum conveying position.

3. The skimming device according to claim 1, in which said Scum receiving trough is in the form of a rotatably positionable pipe having laterally disposed horizontally elongated scum receiving openings.

4. The skimming device according to claim 1, in which the tank has a center pier for rotatably supporting the raking structure, and in which said stationary overhead supporting means for the trough comprise a bridge construction between the tank wall and the center pier.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,062,988 Callow Dec. 1, 1936 2,067,277 Miick Jan. 12, 1937 2,078,266 Morehead Apr. 27, 1937 2,086,730 Mick July 13, 1937 2,237,172 Briggs Apr. 1, 1941 2,249,049 Sayers et al. July 15, 1941 2,253,500 Arango Aug. 26, 1941 2,263,167 Dorr et al. Nov. 18, 1941 2,455,338 Lind Nov. 30, 1948 2,473,297 Parker June 14, 1949 2,611,489 Scott Sept. 23, 1952 FOREIGN PATENTS Number Country Date 390,989 Great Britain Apr. 20, 1933 

